Leaf seals are commonly employed to effect a substantially fluid-tight seal between abutting structural components in a turbo machine or other apparatus wherein a high pressure area is present on one side of the structural components and a low pressure area is present on the opposite side thereof. Leaf seals are typically relatively thin, compliant sections which are formed with a bore adapted to slide along a pin fixed to one of the abutting structural components. Where the structural components to be sealed are annular in shape, as in many components of turbo machines, segmented leaf seals are employed, i.e., relatively short, arcuate-shaped leaf seals which abut one another to form an essentially continuous annular seal between the structural components.
Regardless of the particular shape of the structural components to be sealed, leaf seals are movable to a closed, sealing position in which they engage each structural component and seal the space therebetween, and an open position in which at least one portion of the leaf seals disengage a structural component and allow the passage of gases in between such components. In most applications, movement of the leaf seals along the pins to a closed position is effected by applying a pressure differential across the seal, i.e., relatively high pressure on one side of the seal and comparatively low pressure on the opposite side thereof forces the seal to a closed, sealed position against surfaces of the abutting structural components to prevent the passage of gases therebetween.
While leaf seals have found widespread use in turbo machines, their effectiveness in creating a fluid-tight seal is wholly dependent on the presence of a sufficient pressure differential between one side of the seal and the other. During certain operating stages of a turbo machine, the difference in fluid pressure on opposite sides of the leaf seals is relatively low. Under these conditions, it is possible for the leaf seals to unseat from their engagement with the abutting structural components of the turbo machine and allow leakage therebetween.
A relatively small pressure differential across the leaf seals also permits movement or vibration of the leaf seals with respect to the structural components of the turbo machine which they contact. This vibration of the leaf seals, which is caused by operation of the turbo machine and other sources, creates undersirable wear both of the leaf seals and the surfaces of the structural components against which the leaf seals seat. Such wear not only results in leakage of gases between the leaf seals and structural components of the turbo machine, but can cause premature failure thereof.